This disclosure relates to a gas turbine gearbox arrangement that is used to support and rotationally drive accessory drive components, such as a fuel pump, hydraulic pump, generator, lubrication pump and/or starter.
Gas turbine engines for commercial aircraft applications typically include an engine core housed within a core nacelle. In one type of arrangement known as a turbofan engine, the core drives a large fan upstream from the core that provides airflow into the core. One or more spools are arranged within the core, and a gear train may be provided between one of the spools and the fan. A fan case and nacelle surround the fan and at least a portion of the core.
An inlet of the fan nacelle is designed to avoid flow separation. At cruise conditions, a thinner inlet lip is desired to minimize drag and increase fuel economy. The nacelles are sized to accommodate the widest section of engine, which is often dictated by the size of a single accessory drive gearbox. The accessory drive gearbox, which is driven by a spool through a radial tower shaft and angle gearbox, is typically contained within either the fan nacelle or the core nacelle. A fuel pump, hydraulic pump, generator, lubrication pump, starter and numerous other components are typically mounted to the same accessory drive gearbox, which takes up significant space. As a result, the diameter of the nacelle housing the accessory drive gearbox and accessory components must be increased beyond a desired size. The larger diameter nacelle results in a thicker inlet lip thereby increasing drag at cruise conditions. Increased nacelle diameter also increases weight and fuel consumption. What is needed is a gas turbine engine design with a reduced diameter nacelle.